The present invention relates to a rainbow projector adapted to project rainbow image onto walls of store, stage, a place of party, etc.
It has been principally well known to direct parallel rays coming from a light source into a prism and then to project a spectrum thereof onto a wall or like as a rainbow image. However, no rainbow projector has ever been known, which creates a sufficiently vivid rainbow image to be practically useful for stage lighting. According to the above-mentioned principle, light rays emitted from a light source may be converted through a condenser lens into parallel rays which are, in turn, directed into a prism to achieve a rainbow projection. So far as said light source is a point source, however, no vivid rainbow image can be obtained, since it will be impossible to obtain an adequate quantity of light if said point source is excessively small while it will be more and more difficult to obtain parallel rays as said point source is enlarged. A rainbow projector has already been proposed to which a slit is interposed between the light source and the condenser lens so that the parallel rays exitting from said slit are directed by a spherical lens into the prism. However, such a proposal is not practically useful, since this arrangement is disadvantageous in that said slit results in an extreme reduction of light quantity and the spherical lens of a relatively large diameter determined by a length of said slit will be necessary.